AB1238 LONG-TERM EFFECTIVENESS AND PREDICTORS OF NERIDRONATE TREATMENT OF TYPE I COMPLEX REGIONAL PAIN SYNDROME (CRPS)
Authors: G. Adami, D. Gatti, A. Fassio, V. T. Braga, C. Benini, O. Viapiana, D. Bertelle, M. Rossini
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Complex Regional Pain Syndrome (CRPS) is a painful disease that can lead to chronic pain and disability. Bisphosphonates are largely used in the real-life for the treatment of CRPS, but data on long-term effectiveness and its predictors are lacking. <h3>Objectives</h3> The aim of the present study is to describe the real-life effectiveness of IV neridronate on both pain and long-term disability in patients with type I CRPS. Secondary objective is to determine the factors associated with long-term disability and response to treatment. <h3>Methods</h3> We conducted a longitudinal observational study on patients with type I CRPS treated with IV neridronate (400 mg over 4 days). Clinical and demographic characteristics were collected at baseline, after 3 months (M3) and after 12 months (M12) from treatment. Mixed-effect analysis was used to determine the effect of treatment on VAS pain. Multivariable logistic regression was employed to determine the factors associated with long-term response to treatment. We determined "responders" and "early responders" to be those who achieved a ≥50% VAS score reduction between (baseline/pretreatment) and M12 (responders) and M3 (early responders). We defined "excellent responders" based on full recovery from loss of motion at M12 AND VAS pain at M12 less than 20 mm (excellent responders were those patients with mild/moderate/severe loss of motion at baseline who had none loss of motion at M12 AND VAS pain less than 20 mm). <h3>Results</h3> 103 patients with type I CRPS treated with IV neridronate were included in the study. Mean VAS pain decreased significantly at M3 (79.1 mm to 33.1 mm, -45.9 mm, 95% CI 40.1 to 51.8) and M12 (79.1 mm to 17.5 mm, -61.6 mm, 95% CI 55.3 to 67.9) <b>Figure 1A</b>. Hyperalgesia and allodynia resolved in 84.3% and 88.1% of patients at M12. Loss of motion resolved in 53.5% of patients. The predictors of "excellent response" at M12 were: gender (male better than female), predisposing event to CRPS (no event being better than any predisposing event), site of CRPS (lower limb being better than upper limb), and early response at M3 on VAS pain (2.5 times the chance of being excellent responder every 10 mm decrease). Predictors of excellent response are presented in <b>Table 1</b> (binary logistic regression analysis). <b>Figure 1B</b> shows the long-term VAS pain reduction with IV neridronate in patients with or without complete recovery from functional disability ("excellent responders"). <h3>Conclusion</h3> In this real-life study neridronate was associated with rapid and progressive improvement of symptoms of CRPS which was maintained up to 3 years of follow-up. The predictors of excellent response were early response, lower limb localization, absence of predisposing events and male gender. <h3>REFERENCES:</h3> NIL. <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> Giovanni Adami Speakers bureau: Theramex, Eli-Lilly, BMS, Amgen, UCB, Fresenius Kabi, Galapagos, Davide Gatti: None declared, Angelo Fassio: None declared, Vania Teresa Braga: None declared, Camilla Benini: None declared, Ombretta Viapiana: None declared, Davide Bertelle: None declared, Maurizio Rossini: None declared.